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How do you force a patina on stainless steel?

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I have been combing the forums for a while now and have been very drawn to the beautiful forced patinas that i have been finding. What can I use to force a patina on my CRKT Mirage? I believe it is AUS-6 Stainless but please correct me if I am wrong.

i've done this to my zdp stretch with the stuff used to descale (is this the right word ?) professional dishwashing machines, the bottle said "synergic mix of acids". it was long and i had to heat the liquid a bit to speed it a little.

the blade shows a nice grainy texture and is dull grey, i buffed it to a lighter tone with 0000 steel wool, from what i've read ferric chloride gives a more uniform and darker result.

i've done this to my zdp stretch with the stuff used to descale (is this the right word ?) professional dishwashing machines, the bottle said "synergic mix of acids". it was long and i had to heat the liquid a bit to speed it a little.

the blade shows a nice grainy texture and is dull grey, i buffed it to a lighter tone with 0000 steel wool, from what i've read ferric chloride gives a more uniform and darker result.

So if I cannot get my hands on some ferric chloride what would you suggest I use as a substitute? I am not sure where I can get this^
-Thank you by the way for the tip and insight

+1 on ferric chloride.
I've used this to patina blades before, with reasonable results.
When I say reasonable, I mean probably the best result possible on stainless steel, I don't think it's possible to get a patina like carbon steel acquires, bit it's darn close.
The stumbling block for me was the fact that I couldn't get a realistic patina on the whole blade, because I couldn't disassemble the knife.
This meant that the tang area was mirror polished while the blade was patinated, didn't look right.
The other option would be to dip the knife further into the solution, but then it would attack the bolsters and liners too and possibly ruin them.

If you can think of a way around this problem, ferric chloride should do what you want.
Finding it is no trouble, just search for 'circuit board etchant'.

+1 on ferric chloride.
I've used this to patina blades before, with reasonable results.
When I say reasonable, I mean probably the best result possible on stainless steel, I don't think it's possible to get a patina like carbon steel acquires, bit it's darn close.
The stumbling block for me was the fact that I couldn't get a realistic patina on the whole blade, because I couldn't disassemble the knife.
This meant that the tang area was mirror polished while the blade was patinated, didn't look right.
The other option would be to dip the knife further into the solution, but then it would attack the bolsters and liners too and possibly ruin them.

If you can think of a way around this problem, ferric chloride should do what you want.
Finding it is no trouble, just search for 'circuit board etchant'.

So, if i can take apart the blade without ruining it (or another method), how long should i have the blade in the solution for and what should I use to cancel the reaction?

Do you still have the blade you did this to or have any pics to show? Just curious

The solution I used was used for other stuff too, so it was probably partly 'spent' by the time I etched the blade.
Also, the temperature of the solution affects etching time, hot solution etches faster. Cold solution will work just as well though, and because it reacts slower, you have more control over the end result. Also, using it cold means you don't have to heat this rather nasty solution, which is probably more trouble than it's worth.
The composition of the steel will also greatly affect the etch time.

Ok, with those disclaimers aside, I'd estimate that I probably etched for around five minutes or so.
It was many years ago, so my memory is fuzzy, but that's a ballpark time.

The process itself is very easy:
Put the blade in a plastic container of ferric chloride
Leave for a few minutes
Take the blade out, rinse in water (it gets a sort of greyish film on it that wipes off with your fingers)
Repeat until it's looking how you want it to look.
(optional) sand the surface lightly to enhance the 'vintage' look.

I'm afraid I don't still have the knife, or any pictures of it. Because of the shiny tang areas, the knife just looked weird, so I junked it.

I would describe the appearance of the etched surface as carbon steel that is old but well cared for.
The ferric chloride does not cause pitting, it just gives an even dull grey surface.
I assume this is similar to what happens to carbon steel over time, except the etchant is water and oxygen. Barring any horrific accidents or maltreatment, carbon steel will go from a mirror polish to an even matte grey over time.

When I tried this before, I was hoping to replicate the look of the fruit knives of old (carbon steel main blade and a smaller sterling silver bade for fruit) but with the advantages of stainless steel.
The plan was to etch the main blade but leave the small blade polished, to resemble carbon steel and silver.

I'd still love to do this actually, but I don't know how to disassemble and then reassemble the main pivot on a slipjoint.

If someone would like to chime in and explain how to do this, I'm sure both myself and Deadfall27 would appreciate it

I just tried some Sodium Bisulfate on a stainless cheese knife to see what would happen. I'll post pics when I figure out how to and when the other side of the blade is finished. The blade is dark and is not what i expected...I kinda like it!
45 min in an acid bath of Sodium Bisulfate, who knew?

Edit:
I apologize for the crappy pics, my camera is dead and I have no batteries right now, I had to use my phone
So I went ahead and tested the acid on the cheese knife. In my haste, I forgot some before shots. anyway, it wasn't as dark as previously thought, I will end up doing it again I believe, but I like it nonetheless. Here ya go, tell me what you think:

That's not bad!
It looks like the sodium bisulfide gives a less even finish than ferric chloride, but that isn't necessarily a bad thing, because it looks more natural.
I'd love to see a blade treated with ferric chloride first, and then with sodium bisulfide, I think that would give a real vintage look.

One thing I don't think you'll have much success with is bkackening the stainless.
These solutions are etching the blade and thus making it less reflective (and thus appear darker) but I don't think it's possible to get it darker than that.

The dark stains you see on carbon steel blades are a black oxide of iron formed during the rusting process.
We can get the dulling effect with chemicals, but I don't think there's a way to 'stain' stainless steel.
The chemical etchants give an effect more similar to bead blasting.
I think that the etched surface closely resembles the color of an old carbon steel blade, but a blade that has been cared for and hasn't been allowed to rust.

The black oxide is the 'stain' that's left behind after removing orange rust, or formed by contact with fruit acids for example.
Neither of these things really apply to stainless, although most stainless seteels will rust to an extent if not properly cared for.

Did you try lightly sanding the blades after etching?
To me, that really seems to help the blade look old, because it gives a combination of lighter and darker areas and different surface textures.

Nope, sanding was the final step for me.
It's best to use a reasonably fine grit, 600 or so, and gently 'card' the surface under running water, just to remove some of the grey from the surface.
I wonder if a wash of black ink before sanding would enhance the effect?

I really want to try this again now
Trouble is, I'd only want to do it on a slippie, and I don't think I'd be able to disassemble and then reassemble it neatly.

Maybe I could carefully mask the areas I don't want the etchant to touch with a small artist brush and some nail polish?
Hmm...

During etching of the avtual PCB (electronics), if it's manual, we use permanent marker to line the part of copper to keep them intact. However, the longer it's in the ferri chloride, the solution might 'eat' metal from side & underneath marker (from the non marked areas).

I've lost some finer lines on the circuit this way, & had to connect them with thin wire + soldering

There's been a time or two, when I could've seen a practical use for darkening a stainless blade. In particular, when a buddy and I used to go fishing years ago, more than once I wished for a less shiny blade in the Texas summertime sunlight. The glare from a shiny blade, under that circumstance, feels like a laser beam in the eyes.

And there's nothing wrong with just doing it for the look, too. To each his own.

Just an update on this, I got the same results as ferric chloride by trying electrolysis.
I used a benchtop power supply and a mug of salt water.
The knife was the anode (in this case -ve) and a spoon for the cathode, although pretty much anything metal will do, preferably something with more surface area than the blade. I used a scotchbrite pad to clean the sludge iff the surface periodically.
It took longer than ferric chloride, and the results were slightly less even, but it's pretty much the same, and no need for nasty chemicals.
The blade went very dark, and I sanded it lightly to lighten it up a bit.